A medical pump, comprising: a fluid housing having a plurality of intake openings, sealed by at least one intake valve, and an outlet opening sealed by an outlet valve; a piston which is sealing the fluid housing and connected to a drive mechanism, the drive mechanism pulls the piston to draw fluid from one of the plurality of intake openings and pushes the piston to discharge the fluid into the outlet opening; and a selecting valve enclosing at least two tubes, each providing fluid to one of the plurality of intake openings, wherein the selecting valve closes one of the at least two tubes while opening another of the at least two tubes.